/Engine/Source/Runtime/Experimental/Chaos/Public/GeometryCollection/Facades/CollectionTransformSelectionFacade.h
Get bones filtered by the level as they would be in the editor; i.e., the bones with level <= the target Level, but with some additional logic for filtering, etc
[TArray](API\Runtime\Core\Containers\TArray)< int32 > GetBonesByLevel ( const int32 Level, bool bOnlyClusteredOrRigid, bool bSkipFiltered ) const